clustering vs concentration

clustering

noun
  • The grouping of a population based on ethnicity, economics or religion. 

  • The undesirable contiguous grouping of elements in a hash table. 

  • A grouping of a number of similar things. 

  • A prewriting technique consisting of writing ideas down on a sheet of paper around a central idea within a circle, with the related ideas radially joined to the circle using rays. 

adj
  • Forming a cluster. 

concentration

noun
  • The proportion of a substance in a whole. 

  • The act, process or product of reducing the volume of a liquid, as by evaporation. 

  • The act or process of removing the dress of ore and of reducing the valuable part to smaller compass, as by currents of air or water. 

  • The direction of attention to a specific object. 

  • A field or course of study on which one focuses, especially as a student in a college or university. 

  • The amount of solute in a solution measured in suitable units (e.g., parts per million (ppm)) 

  • The matching game pelmanism. 

How often have the words clustering and concentration occurred in a corpus of books? (source: Google Ngram Viewer )